Numerous situations exist where fluid is piped under pressure to a number of final delivery points in which the distribution system is primarily concerned with the distribution of fluid over a given area. Typical situations for this are agricultural sprinkler irrigation systems and home garden sprinkler systems.
In many systems, maintenance of a desired level of fluid flow to certain areas within the system requires a certain minimum pressure at the system supply valve. For example, a given source pressure may be necessary to pump water to sprinklers located at the crest of a hill. Such requirements prevent the final volume rate of flow of fluid in such a system from being lowered by merely adjusting the system supply valve.
Since these systems are typically very large, however, substantial fluid savings can generally be obtained if only the required amount of fluid is discharged at each final delivery point, e.g., each sprinkler head. In order to limit the volumetric delivery rate at each final delivery point, flow restrictors such as elastomeric flow restrictors, are used to obtain a relatively constant fluid volumetric delivery rate over a relatively broad range of initial input delivery pressures. As described in U.S. Pat. Nos. 4,105,050 and 4,609,014, the relatively constant volumetric delivery rate results from the elastomeric flow restrictors changing in shape in response to the input pressure of the fluid against the restrictors. Many existing systems, however, do not include such restrictors and, therefore, the restrictors need to be added to the systems. Since the restrictors must be installed at each final delivery point, it is only practical to install such restrictors if the installation procedure can be quickly and easily performed, and if the restrictors themselves are inexpensive.
Even where the original delivery system incorporates flow restrictors, it may later be found that too large or too small a volume of fluid is being delivered to one area of the system. It is then desirable to be able to change the fluid restrictors utilized at the final delivery points in that area of the system to increase or decrease volume of fluid delivered to that area, without affecting the volume of water delivered to other areas within the system. Likewise, even in properly running systems, it is sometimes desirable to change the volume of fluid delivered throughout the system, either due to a change in the level of seasonal precipitation or a change in the delivery target, e.g., a change of crops.
Since such a restrictor is needed in the field of irrigation, it is desirable that the restrictor be able to be utilized in connection with a wide variety of sprinkler heads. Although sprinkler heads come in a range of shapes and sizes, many are provided with a screen seated within the mouth of the fluid flow channel formed by the sprinkler head fitting to which the sprinkler head is attached. To permit these screens to be used interchangeably in a variety of systems, the mouths of most sprinkler head fittings are of a standard size.
What is needed is a fluid flow regulator which is simple, inexpensive, easy to install and replace, and is adapted to function with a wide variety of existing sprinkler systems.